X-kay tube adapted for sigh vol t ags



Jan. 10, 1928. c. T. ULREY x-RAY TUBE ADAFI'ED FOR HIGH VOLTAGE Filed Sept. 4. 1925 W. R m L mu N n Y A L C ATTORNEY Patented .l 10, 19,28. 1, 5

M N [T s.

CLAY'IQN TBIIDLE ULREY, OF Eftfflll ORANGE, NEW JERSEY, ASSIGNOR T WESTING- I-IOUt-EEE LAMP OUMPAIIQ'Y, A. CORPUlti-l'lltlll' 011'" IEENNSYLVANI A.

STATES PATENT OFFICE.

TUBE nnan'rnn non siren 'vonrnen.

Application filed September 4, 1925. serial No. 54,446.

'lhis invention relates to it-ray tubes and thereof at points adjacent the juncture otthe more particularly to a high "voltage X-ray electrode arms and the spherical portion of tube in which no severe electrical stresses the envelope. are impressed upon the glass Walls oi the A more specific object of: my invention is t envelope thereof. to provide an l l-ray tube With a relatively High voltageliiofay tubes of usual'desiun short cathode arm anduirelatively long embody a large spherical bulbous portion anode arm whereby the electrical stresses and CWO oppositely ester; ng arnis o'l subupon the envelope Where the electrode stems stantially equal length, which support the are spaced closely therefrom are reduced to l electrodes oi the tube. Tubes oil this na 8. minimum.

ture frequently puncture because of the se- Other objects of my invention Will be apvere electrical stresses upon the Walls parent from reading the following detailed of the tube, especially at a point near the description. juncture of the cathode arm with the bulb- Referring to the drawing, for a better ill one portion (at the envelope. The reason understanding oi the invention, the single for the high electrical stresses at this porfigure illustrates a longitudinal sectional tion ot the tube is that on the outside of view of an lit-ray tube embodying the inthe tube there is a leakage ctu'rent trein one vention. electrode terminal to the other, thus caus An Kitty tube embodying my invention ing a drop in potential over the glass surface may comprise a main spherical bulbor chanr approximately proportional to the distance becQ having! outwardly and oppositely from. either terminal. It the voltage drop tending arms and 4-. The arm 3 which across the electrodes assumed to be 250,000 may be termed the cathode arm, is adapted volts, then is obvious thatthe potential to house the leading-in Wires 5 and 6 which di'l'l'erence between the and the netal are connected. to a cathode 7 ol the thermiof either electrode, assuming the potential onic type. .l-t focusing cup 8 of usual die of the electrodes to be the same throughsign is provided to uniformly distribute the 50 out their lengths, will vary in proportion electr 1554 coming troni the cathode 7 over to the distance along the surface of the the face of the large disk target 9. A central bulb When moving; from one terminal to the projection 11 extending outwardly beyond other. it the distance oil. the juncture point the edge of the tocussing; cup andpositioned of either arm with the spherical portion of centrally thereof and connected to one of B the envelope one-third of the total disthe cathode leads assists in dispersing the tance along the surface of the envelope beelectron stream so that the electrons uni- 35 tween the electrode terminals, then. the volttorinly strike the face of the target. The age at such. point would be one third oi purpose of this construction is to ei'lectively 250,000 volts or about (l3,000 volts. Uwinn; dissipate the heat generated in the large to the close spacing otthe electrode shanlt disk target through electronic impact. from the glass Walls this point as Well "llhe target 9 is supported by a stem 15% as the small radii of curvature of the arm, "which in turn is suitably secured to a sleeve this electrical stress upon the I may 13 mounted upona reentrant g1 tube 1% prove too great for the glass to "Withstand sealed to the anode hfllld. pp the same with the resultthat puncturing Especial attention is d rected to the coin occurs. paratlve lengths of the cathode arm 3and According to my invention, 1 reduce the the anode fitllll'l, the former being relatively length of the cathode arm to such anlextent short as compared With the latter. The as to cause a reduction in the potential imvantage of this construction Willbe' appre'ci pressed upon theiglass at the point where ated inore tully from the following ex planait joins the spherical portion of the envelope tion and turtherinoreconst tutes the inoper- 50 so that danger of puncturing is reduced. tantilieature otthe present invention. Pref Therefore, it I an object of my invention erably the arm Qlis about one eighth of the to so d n the iyelope ot an 1y tube total overall lengthoi the tube. ri t/eves, as to prevent puncturing oi the glass walls the relative proportions of the arrnmay be ivention, a brief description will first be given as to the construction of the usual form of high voltage X-ray tube, partrcularly With reference to the structural details thereof Which are the cause of such tubes frequently puncturing. Tubes of the usual designhave their cathode and anode arms o't substantially, equal length. Viewing the li ure shown in the'drawing and considering the arm at to be approximately hall the length therein shown, and the cathode arm I} of substantially equal length thereto, an X- ray tube of usual design is then obtained in so far as the envelope construction is concerned. Suppose it be assumed that the distance from, the end of the anode arm to the end of the cathode arm is thirty inches and the length of the arms are ten inches and that an operating potential of 250,000 volts is impressed across the QlCClil'OCiiCS. Furthermore, that the potential drop over the glass surface between the ends of the OIGCtI'OClBtLIHIS lS substantially unilorm and 't-hatthe potential drop along the length of the electrodes from the electrodes proper to the ends of the arms'is negligible, then the potential difference between the cathode and the glass of the tube at the point of intersection of either arm with the spherical portion of the glass envelope is about 80,000-

volts. If it is assumed that the cross sec-- tron of the necks are relatively small say 1 to 2 inches in diameter, and this is usually the case, then puncture may very easily occur atthe juncture points of the arms with the bulbous portion of the envelope because of the nearness of the electrodes or their stem or leads thereto and the relatively small radii of curvature of the glass at such points.

For the purpose of comparison, let it be assumed that the overall longitudinal dimension of the tube in the drawing is 30 inches, that is ,the same as the tube in thcexamplc given in the preceding paragraph, and that lit) ' short, say 3 the diametcr of the main bulb is the same in each instance. Now instead of making the cathode arm 10 inches in length as in the previous illustration, assume that it. is very inches. Obviously then, the potential stressat the intersection of the cathode arm with the spherical arm will be considerably less than that in the usual tube,

sinceavith an impressed potential of 250.000

volts, the electric stress will be 3450 of 250,000 voltsor 250,000 volts, which stress considerablyless than the 80,000 volt stress prevailing in the usual tubes.

'It 1s to be understood that although the electrical stress at the juncture of the anode arm with the spherical bulb may be increased by reason of my construction, I have observed that puncture does not occur at this end of the tube but usually takes place, it at all, atthe cathode end. The reason for this is not fully understood but may be attriljiutcd to electronic impact upon the glass which may be already in a strained condition by reason of the large electrical stress. Owing to the fact that the electrons moving in the direction of the anode are detlccted thereto. itis apparent that there is very little it any electron impacts upon the walls of the tube at the anode end, nnJticularly at the juncture of the anode arm with the spherical portion of the envelope.

The electrical lield inside the tube is such as to cause an accumulation of electrons on the inside surface of the glass near the cathode extension of the bulb. This, however, does not produce a dangerous strain on the glass in this region in a tube of: my construction since the outside surface also acquires an accumulation of negative electricity by leakage from the cathode terminal.

Although I have described what I now consider the preferred embodiment ol: my invention, it is to be understood that the same is merely illustrative and that modifications may occur to those skilled in the art within the spirit and scope of the appended claims.

What is claimed is:

1. An X-ray tube comprising a main spherical bulb portion and a pair of outwardly extending arms, an anode and a. thermionic cathode supported. by said arms, said cathode supporting arm being materially shorter than the anode siu'iporting arm, and a foeussing device surrounding said cathode and insufficient in size to intercept electrons emanating from said anode, whereby puncture of the tube by electrical stresses is diminished.

2. An X-ray tube comprising a main chamber and anode and cathode arms outwardly extending therefrom, an anode and a. thermionic cathode partly surrounded by said arms, said cathode arm having a length less than the length oi? said anode arm and about equal to one-cighth the overall length of: said tube, and a. locussing cup sin-round,- ing said cathode andv insutlicicnt in size to prevent electronic honibardment ol' the walls ot the tube adjacent the cathode arm.

3. An X-ray tube comprising a. main spherical. chamber, an arm |)l'0jtlt.ldll l,f themfrom and materially longer than the diameter of said chamber, another arm extending from said chamber and shorter than the diameter of said chamber, an anode and a. thermionic cathode supported by said arms, and a focussing device surrounding said cathode and insufficient in size to prevent electronic bombardment of the walls of the tube adjacent said cathode.

l. An X-ray tube comprising an envelope having a spherical chamber and a pair of:

till

arms extending outwardly from said chamber and in opposite directions, an anode supported by and sealed to one arm and a thermionic cathode supported by and sealed to the other arm, the overall. length of said tube being such as to prevent a discharge over the surface of said envelope between the terminals of said anode and. cathode the cathode arm being of such length With respectto the overall length of the envelope that the electrical stress a minimum at the point Where said arm joins the spherical chamber when a maximum potential is ap plied to said tube, and a focussing device surrounding said cathode and of insufficient size to intercept electrons emanating from said anode.

5. A11 X- 'ay tube comprising an envelope having a spherical. compartment and outwardly extending and oppositely disposed arms secured to said compartment, an anode and a thermionic cathode Within said eom partment, electrical conductors connected to said anode and cathode and. hermetically sealed Within the outer ends of said arms,

said arms being of unequal length the shorter of said arms being of such length with respect to the overall length of the tube as to prevent detrimental electrical stress at its juncture with the spherical compartment and a iiocussing device surrounding said cathode and iusuliicient in size to prevent electronic bombardment of the Walls of the tube adjacent the cathode.

(3. An X-ray tube comprisii'lg a bulb, a cathode and anode mounted in said bulb, means for heating said cathode and means associated. with. said cathode for dispensing the electron stream emanating from the cathode so that the electroi'is uniformly strike the face of the target, said target consisting oil a relatively thin disk of large size and so proportioned as to effectively radiate the heat generated therein through electronic impact Without requiring external cooling means.

In testimou whereof. I have hereunto subscribed un name this 3rd day of tieptemben 1925. i

CLAYTON TRIDLE ULREY. 

